IL-33 was higher in non-smokers (61.09 pg/mL, IQR 0–1346.06) as compared to stable COPD (0 pg/mL, IQR 0–33.99, p = 0.021), and there was a tendency, as compared to smokers, but it did not reach statistical significance (4.08 pg/mL, IQR 0–72.53, p = 0.860, Figure 1B). Here, IL33 is linked to chronic obstructive pulmonary disease.